摘要:

AP Ablation and the “W Sign.”introduction:The aim of this study was to evaluate the efficacy of radiofrequency (RF) ablation of the atrial insertion of left‐sided aceessory pathways with guidance by a specific morphologic characteristic of the local electrogram, which we call the “W sign.” This represents the shortest local atrioventricular (AV) interval during sinus rhythm in patients with manifest preexcitation or the shortest local VA interval during AV reciprocating tachycardia and/or ventricular pacing in patients with concealed accessory pathways.Methods and Results:The transseptal technique was used in 31 patients (18 men, 13 women; aged 32 ± 13 years), and RF ablation of 33 accessory pathways (26 manifest and 7 concealed) was attempted. Patients presented with palpitations (n = 16), presyncope (n = 10), or syncope (n = 5). The clinical arrhythmia was AV reciprocating tachycardia (n = 24) or atrial fibrillation (n = 7). In 21 patients (68%) electrophysiologic study and RF ablation were performed at a single session. Accessory pathways were left posteroseptal (n = 5) or left free wall (n = 28). The “W sign,” formed from merging of the local atrial and ventricular electrograms, was identified at all successful sites prior to ablation. Ablation was successful in all patients. A median of 7 RF lesions were delivered per patient. The fluoroscopy time was 76 ± 48 minutes; total procedure time was 5.4 ± 1.9 hours. No significant complications occurred. Early recurrence (≤ 24 hours) occurred in I patient; during 6 ± 4 months, accessory pathway conduction recurred in another patient.Conclusion:We conclude that RF ablation of the atrial insertion of left accessory pathways can be very successful when gui

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00383.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00384.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Stability, An ICD Detection Criterion.introduction:The purpose of this study was to review a new implantable cardioverter defibrillator (ICD) detection criterion, stability, to determine if it can effectively discriminate rapid rhythms of atrial fibrillation from ventricular tachycardia. Inappropriate shocks for rapid atrial fibrillation limit the acceptance of ICDs. The advent of an additional detection criterion, stability, has been postulated to be of value in discriminating rapid atrial fibrillation, which may not warrant treatment, from ventricular tachycardia, which obviously does warrant therapy delivery.Methods and Results:Twenty‐six patients were studied during 32 episodes of rapid atrial fibrillation and 24 episodes of monomorphic ventricular tachycardia below 220 beats/min. Each rhythm was repeatedly evaluated by the device at each of the seven stability values available (8, 16, 23, 31, 39, 47, and 55 msec) and then classified as stable or unstable. Upon completion of this acute study, 32 ICD patients bad the stability feature activated and were followed for proper arrhythmia treatment by the device. Using stability windows from 8 to 47 msec, all atrial fibrillation rhythms were appropriately classified as unstable. Three of 6 were classified correctly for the 55‐msec window. All ventricular tachycardia rhythms were appropriately classified as stable for all stability windows from 8 to 55 msec. Clinical follow‐up confirmed appropriate therapy delivery when coupled with sustained rate duration (SRD). Thirty‐two patients followed for 292 patient‐months had no episodes of untreated ventricular tachycardia with 428 successfully classified as stable and treated. Only three episodes of suspected atrial fibrillation resulted in therapy delivery as the rhythm duration exceeded the SRD of 30 seconds.Conclusions:The CPI Ventak PRx ICD is highly reliable in appropriately classifying atrial fibrillation as unstable and monomorphic ventricular tachycardia as stable for most stability windows evaluating tachycardias below 220 beats/min. As a result, when testing of atrial fibrillation is not possible, we recommend the routine programming of this stability feature at the 31‐msec window with an SRD of 30 seconds. The reliability of this device in discriminating atrial fibrillation from monomorphic ventricular tachycardia may have important clinical implications for other tiered therapy ICDs with this feature as well as for future ICDs in

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00385.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

RF Lesions From Cooled Electrode.Introduction:The delivery of radiofrequency (RF) energy through conventional catheter electrodes is often associated with coagulation necrosis at the tissue‐electrode interface, with resultant impedance rise and limited lesion size. This study was performed to examine the effects of catheter tip cooling during RF delivery, to test the hypothesis that such cooling would decrease the likelihood of impedance rise and allow the creation of larger endomyocardial lesions.Methods and Results:The experiments were performed in eight open chest, anesthetized sheep. RF lesions were created within both ventricular chambers of each animal through a catheter tip that could he cooled with a saline perfusate. Assignment of cooled versus non‐cooled RF delivery to either ventricle was alternated from one animal to the next. In each set of experiments, lesion volumes relative to the mode of RF delivery were compared. The mean power delivered via the cooled electrode (22.04 ± 4.51 W) was significantly higher than that delivered via the noncooled electrode (6.10 ± 2.47 W; P<0.001). The mean duration of RF delivery was 42.7 ± 11.2 sec for noncooled lesions versus 49.2 ± 6.8 sec for cooled lesions (P<0.01). Mean lesion volume was 436.07 ± 177.00 mm3for noncooled RF delivery versus 1247.78 ± 520.51 mm3for cooled RF delivery (P<0.001). This significantly larger lesion size with cooled RF delivery was associated with no instance of impedance rise in 27 attempts versus 11 impedance rises in 28 attempts with noncooled RF (P<0.001).Conclusions: Delivery of RF energy through a cooled catheter tip allows the creation of larger endomyocardial lesions by limiting the occurrence of impedance rise despite the delivery of greater energy. These observations suggest that, under certain conditions, resistive tissue heating at a distance from the site of current delivery may play an important role in RF ablatio

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00386.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

90‐μF and 120‐μF Biphasic Pulse Transvenous Defibrillation.Introduction:Capacitance is known to influence defibrillation. Optimal biphasic waveform capacitance for transvenous unipolar defibrillation systems in man is currently being defined. In an effort to improve defibrillation efficacy, we examined the relative defibrillation efficacy of a 65% tilt biphasic pulse from a 90‐μF capacitor compared to a 65% tilt biphasic pulse from a 120‐μF capacitor in a prospective, randomized fashion in 16 consecutive cardiac arrest survivors undergoing defibrillator surgery.Methods and Results:The transvenous unipolar pectoral defibrillation system uses a single endocardial RV anodal defibrillation coil and the shell of an 80‐cc volume (88 cm2surface area) pulse generator (Medtronic Model 7219C PCD “active CAN”) as the cathode for the first phase of the biphasic shock: RV+→ CAN−. Defibrillation thresholds for each capacitance were determined prospectively in a randomized fashion. The defibrillation threshold results for the 90‐μF capacitance were: leading edge voltage 383 ± 132 V; stored energy 7.4 ± 5.0 J; and resistance 57 ± 10 ω. The results for the 120‐μF capacitance were: leading edge voltage 315 ± 93 V (P = 0.002); stored energy 6.5 ± 3.7 J (P = 0.21); and resistance 57.0 ± 11 ω (P = 0.87).Conclusions:We conclude that 90‐μF, 65% tilt biphasic pulses used with unipolar pectoral defibrillation systems have equivalent stored energy defibrillation efficacy compared to 120‐μF, 65% tilt pulses. Use of lower capacitance is possible in present implantable defibrill

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Propagation in a Modeled Ischemic Border Zone.Introduction:It is suggested that heterogeneous extracellular potassium concentration, cell‐to‐cell coupling, and geometric nonuniformities of the ischemic border zone contribute to the incidence of unidirectional block and subsequent development of lethal ventricular arrhythmias.Method and Results:A discrete electrical network was used to model a single cardiac fiber with a [K+]egradient characteristic of an ischemic border zone. Directional differences in propagation were evaluated by creating discrete regions with increased gap junctional resistance within the [K+]egradient. Furthermore, the effect of homogeneity/heterogeneity of cell length on impulse propagation through the [K+]egradient in the presence of increased gap junctional resistance was evaluated. The results indicate that failure of impulse propagation occurs at the junction between partially uncoupled and normally coupled cells. Furthermore, propagation failure was more likely to occur as the impulse propagated from a region of high [K+]eto low [K+]e. Heterogeneity in cell length contributes to the variability in the occurrence of unidirectional and bidirectional block.Conclusions:The onset of cellular uncoupling in an ischemic border zone may interact with the inherent [K+]egradient leading to unidirectional conduction block. This mechanism may be important for the generation of reentrant arrhythmias at the ischemic border z

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Left Anterior Fascicular Tachycardia.Introduction:A 45‐year‐old man with idiopathic ventricular tachycardia (VT) having a right bundle branch block configuration with right‐axis deviation underwent au electrophysiologic test.Methods and Results:Mapping demonstrated a site on the auterobasal wall of the left ventricle where there was an excellent pace map and an endocardial activation time of ‐20 msec, hut radiofrequency catheter ablation at this site was unsuccessful. At a nearby site, a presumed Purkinje potential preceded the QRS complex by 30 msec during VT and sinus rhythm, and catheter ablation was effective despite a poor pace map and an endocardial ventricular activation time of zero.Conclusion:Idiopathic VT with a right bundle branch configuration and right‐axis deviation may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may he more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this t

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

WPW Variant.Introduction:The differentiation between a nodoventricular fiber and an accessory atrioventricular (AV) pathway with long conduction times and decremental properties could he very difficult even at detailed electrophysiologic study.Methods and Results:A 20‐year‐old male with a history of a wide QRS tachycardia underwent electrophysiologic study. Baseline intervals were normal. There was evidence of dual AV pathways, and a sudden increase in AH interval was associated with the emergence of a delta wave. The atrio‐delta interval showed a progressive prolongation. The preexcited QRS complex was typical of a posteroseptal pathway, and the earliest ventricular activation site was recorded at the posteroseptal region. Retrograde conduction was exclusively over the normal conduction system. During ventricular extrastimulation, a sudden increase in HA interval was associated with anterograde conduction over the accessory pathway. The intervals between the stimulus artifact and the onset of the delta wave during atrial pacing from two atrial sites (S‐Delta) were compared with those between the retrograde atrial electrogram on the His channel and the onset of the delta wave during ventricular pacing (A2HB‐Delta). When pacing from the proximal coronary sinus, the shortest S‐Delta interval did become shorter than the longest A2HK‐Delta interval (155 vs 170 msec).Conclusion:The finding that the S‐Delta interval could become shorter than the A2HB‐Delta interval provides strong evidence that this accessory pathway was not connected to the AV node hut arose directly from the atrial tissue of the pos

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Inappropriate Sinus Tachycardia. Inappropriate sinus tachycardia is an ill‐defined clinical syndrome characterized by an increased resting heart rate accompanied by an exaggerated response to exercise or stress. It is not associated with underlying structural heart disease. The mechanism may involve a primary abnormality of the sinus node demonstrating enhanced automaticity or, alternatively, a primary autonomic disturbance with increase sympathetic activity and enhanced sinus node β‐adrenergic sensitivity. The diagnosis of inappropriate sinus tachycardia is one of exclusion. It is most common in young females, with a disproportionate number employed in the health care field. Autonomic and electrophysiologic testing may be required in selected individuals to clarify the mechanism and rule out sinus node reentry or right atrial tachycardia. Therapy of inappropriate sinus tachycardia is empiric. Pharmacologic approaches include beta blockers or verapamil. Radiofrequency catheter ablation of the superior portion of the sinus node shows promise as a useful alternative in patients with refractory symp

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Arrhythmias in Children. In recent years, the distinction between the diagnostic and therapeutic techniques used in the assessment and management of pediatric and adult patients with arrhythmias has gradually blurred. Nonetheless, arrhythmias in the pediatric patient are still often different from the adult patient in one of two important ways. First, a variety of arrhythmia mechanisms remain relatively unique to the pediatric population, some because of developmental issues and others because of early presentation of an incessant tachycardia. Second, the presentation and management of certain arrhythmias is sometimes markedly affected by patient age or the presence of structural congenital heart disease. A sampling from each of the above categories is reviewed and discussed.

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00392.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY